1. Field of the Disclosure
The present disclosure relates to a multi-core optical fiber having a plurality of core portions, an optical connector therewith, and a method of manufacturing a multi-core optical fiber.
2. Description of the Related Art
A multi-core optical fiber having a plurality of core portions is assumed to be used for an optical transmission channel which is required to densely house optical fibers in an optical cable and an optical interconnection system in which densely-arranged wirings inside an instrument is required. As the conventional optical fiber, a multi-core optical fiber can be a type that confines light to the core portion by using a refractive index difference between a core portion and a cladding portion which are formed from mediums with refractive indexes different from each other (M. Koshiba, K. Saitoh and Y. Kokubun, “Heterogeneous multi-core fibers proposal and design principle”, IEICE Electronics Express, vol. 6, no. 2, pp. 98-103 (2009), a multi-core holey fiber which has a structure in that cladding portions are periodically formed in pores and can use ultrawideband ranging from a visual light range to a near infrared light range as a signal light (K. Imamura, K. Mukasa, Y. Mimura and T. Yagi, “Multi-core holey fibers for the long-distance (>100 km) ultra large capacity transmission”, Proceedings of Optical Fiber Communication Conference 2009, OtuC3 (2009)), or the like. In these multi-core optical fiber, each of a plurality of core potions is separated from the other by a gap of 40 μm or 50 μm in a cross-section perpendicular to a longitudinal direction, whereby a dense arrangement of core portions can be realized while crosstalk between the core portions is suppressed.
Moreover, a document “Demonstration of multi-core photonic crystal fiber in an optical interconnect”, Electronics Letters, vol. 42, no. 6, pp. 331-332 (2006) by D. M. Taylor, C. R. Bennett, T. J. Shepherd, L. F. Michaille, M. D. Nielsen and H. R. Simonsen, (hereinafter to be referred to as Taylor) discloses a technique of optical transmission with a vertical cavity surface emitting laser (VCSEL) array being used as a signal light source and a multi-core optical fiber being used as an optical transmission channel.
In Taylor, a pitch (gap length) between each adjacent VCSEL elements in the VCSEL array is 62.5 μm. However, fabrication of the VCSEL array in which the VCSEL elements are arranged as closely as such is difficult. In terms of yield rate and fabrication cost, a current realistic pitch of the VCSEL array is about 250 μm. Therefore, when a dense multi-core optical fiber with a pitch between each adjacent two of a plurality of the core portions is being 40 to 50 μm and a realistic VCSEL array being a connection target are to be connected, it is difficult to optically connect each core portion and each VCSEL element.